From 74d8de8fc22c277215873f27868ebc63fa481ee7 Mon Sep 17 00:00:00 2001
From: Maxim Lebedev <git@toby3d.me>
Date: Fri, 29 Sep 2023 20:55:13 +0600
Subject: [PATCH] :technologist: Created ShiftPath urlutil

---
 internal/urlutil/shift_path.go      | 22 +++++++++++++++++
 internal/urlutil/shift_path_test.go | 37 +++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+)
 create mode 100644 internal/urlutil/shift_path.go
 create mode 100644 internal/urlutil/shift_path_test.go

diff --git a/internal/urlutil/shift_path.go b/internal/urlutil/shift_path.go
new file mode 100644
index 0000000..39dbf71
--- /dev/null
+++ b/internal/urlutil/shift_path.go
@@ -0,0 +1,22 @@
+package urlutil
+
+import (
+	"path"
+	"strings"
+)
+
+// ShiftPath splits off the first component of p, which will be cleaned of
+// relative components before processing. head will never contain a slash and
+// tail will always be a rooted path without trailing slash.
+//
+// See: https://blog.merovius.de/posts/2017-06-18-how-not-to-use-an-http-router/
+func ShiftPath(p string) (head, tail string) {
+	p = path.Clean("/" + p)
+
+	i := strings.Index(p[1:], "/") + 1
+	if i <= 0 {
+		return p[1:], "/"
+	}
+
+	return p[1:i], p[i:]
+}
diff --git a/internal/urlutil/shift_path_test.go b/internal/urlutil/shift_path_test.go
new file mode 100644
index 0000000..c0a32f2
--- /dev/null
+++ b/internal/urlutil/shift_path_test.go
@@ -0,0 +1,37 @@
+package urlutil_test
+
+import (
+	"testing"
+
+	"source.toby3d.me/toby3d/pub/internal/urlutil"
+)
+
+func TestShiftPath(t *testing.T) {
+	t.Parallel()
+
+	for name, tc := range map[string]struct {
+		input, expHead, expTail string
+	}{
+		"root":    {input: "/", expHead: "", expTail: "/"},
+		"file":    {input: "/foo", expHead: "foo", expTail: "/"},
+		"dir":     {input: "/foo/", expHead: "foo", expTail: "/"},
+		"dirfile": {input: "/foo/bar", expHead: "foo", expTail: "/bar"},
+		"subdir":  {input: "/foo/bar/", expHead: "foo", expTail: "/bar"},
+	} {
+		name, tc := name, tc
+
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			head, tail := urlutil.ShiftPath(tc.input)
+
+			if head != tc.expHead {
+				t.Errorf("ShiftPath(%s) = '%s', want '%s'", tc.input, head, tc.expHead)
+			}
+
+			if tail != tc.expTail {
+				t.Errorf("ShiftPath(%s) = '%s', want '%s'", tc.input, tail, tc.expTail)
+			}
+		})
+	}
+}